This invention relates to a port security system, and more particularly, but not by way of limitation, this invention relates to an apparatus and method to detect the presence of enemy swimmers in the waters surrounding docks, piers, breakwaters, bridges, or other harbor or estuarial architecture. In greater particularity, the invention relates to an apparatus and method to discover the presence of enemy swimmers as a step in countering the placement of marine mines at ship anchorages.
The protection of merchant and naval ships against enemy action is, of course, an object of all naval powers. As grevious as the loss of a ship is to such naval powers, it is even more lamentable if the loss occurs in a harbor anchorage or at dock side, for an immobile sunk ship prevents the further use of the dock or anchorage for the intended purpose. It is for this reason that a ship at anchor or tied alongside a dock, as it is unloaded or loaded, is in particular peril of enemy attack.
Prior art attempts to prevent such enemy action have for the most part involved apparatus to secure the anchorage from underwater approach. Such devices have included a variety of barriers, fences, nets, and other restrictive devices. While these devices prevent swimmers from approaching the anchorage, they also interfere with the normal movement of the ships using the anchorage. Further, the restrictive devices may be breached without detection.